code: def test_hub_model_builder(self):
      def _fake_model(in_features=10, out_features=10) -> nn.Module:
          """
          A fake model builder with a linear layer.
          """
          model = nn.Linear(in_features, out_features)
          return model
  
      in_fea = 5
      default_config = {"in_features": in_fea}
      model = hub_model_builder(
          model_builder_func=_fake_model, default_config=default_config
      )
      self.assertEqual(model.in_features, in_fea)
      self.assertEqual(model.out_features, 10)
  
      # Test case where add_config overwrites default_config.
      in_fea = 5
      default_config = {"in_features": in_fea}
      add_in_fea = 2
      add_out_fea = 3
  
      model = hub_model_builder(
          model_builder_func=_fake_model,
          default_config=default_config,
          in_features=add_in_fea,
          out_features=add_out_fea,
      )
      self.assertEqual(model.in_features, add_in_fea)
      self.assertEqual(model.out_features, add_out_fea)
  
      # Test assertions.
      self.assertRaises(
          AssertionError,
          hub_model_builder,
          model_builder_func=_fake_model,
          pretrained=True,
          default_config={},
          fake_input=None,
      )
  
file_path: pytorchvideo/tests/test_models_hub_vision_transformers.py
imports: import os
  import unittest
  import torch
  import torch.nn
  from pytorchvideo.models.hub.utils import hub_model_builder
label_desc: Use image node_id 3 for calling the TestHubVisionTransformers obj's underlying member method code with example usage: obj.test_hub_model_builder() and returns: model